Little is known about the association of angiomyolipoma and adult renal-cell neoplasia. We studied the clinicopathologic features of 36 patients with concurrent angiomyolipoma and renal-cell neoplasia from the consultation and surgical pathology files of nine institutions. HMB-45 immunoreactivity was analyzed in both neoplasms. Twenty-five sporadic cases of patients with angiomyolipoma and renal-cell neoplasia and 11 cases of patients with tuberous sclerosis, as defined by Gomez' criteria, had mean ages of 59 and 53 years, respectively, and female-male ratios of 2:1 and 5:1, respectively. The mean size of the angiomyolipomas was 1 cm in the sporadic cases and 3 cm in those patients with tuberous sclerosis (medians: 0.5 and 3 cm, respectively, P =.002). The mean sizes of the renal-cell neoplasms were 5 cm in sporadic cases and 6 cm in patients with tuberous sclerosis (medians: 4 and 5 cm, respectively; P =.88). In both clinical settings, angiomyolipoma was more commonly the incidental tumor. Clear-cell (conventional) renal-cell carcinoma was the most common renal-cell neoplasm in both groups of patients, accounting for approximately two thirds of the tumors. In patients with tuberous sclerosis, 27% of renal-cell neoplasms were oncocytomas, compared with 8% in sporadic cases (P =.15). Papillary neoplasia, chromophobe, and collecting-duct renal-cell carcinoma were found only in sporadic cases. All of the 22 renal-cell neoplasms studied were negative for HMB-45, whereas all 25 angiomyolipomas studied were positive.